(1) Field of the Invention
The present invention relates to a method and an apparatus for cutting an adhesive tape into a circular shape. More particularly, the present invention relates to a method and an apparatus for cutting an adhesive tape joined to a ring frame which is mounted at the time of dicing a semiconductor wafer.
(2) Description of the Related Art
Generally, a surface protective tape is preliminarily joined to the surface of a semiconductor wafer (hereinafter, simply referred to as a wafer), which has been subjected to a pattern forming process, and part of the surface protective tape, which protrudes from the outer circumference of the wafer is cut out along the outer peripheral edge of the wafer. In a state where the whole surface of the wafer is protected with the surface protective tape, a wafer back-side polishing process is performed on the back side of the wafer which is put upside down. After that, an adhesive tape for dicing is joined to the back side of the wafer on which the wafer back-side polishing process has been completed and is integrated with a ring frame for a chip dicing process. At this time, the adhesive tape is joined to the ring frame and is cut in a circular shape by making a cutter come into contact with the adhesive tape joined to the ring frame and revolve once around the center of the ring frame as a base point (see, for example, JP-A 11-3876 (1999)).
However, as also described in JP-A 11-3876 (1999), since the adhesive tape for dicing is cut while pressing the cutter against the ring frame, the path of cutting by the cutter remains in the face of the ring frame. Consequently, even when the ring frame is made of, for example, metal or resin, after repetitive use, at the time of cutting, the cutter enters the cutting path of the cutter, formed during the past cutting operations. As a result, there is a case such that the course of the cutter is forcedly changed and a cutting start point and a cutting end point do not coincide with each other. In such a case, the adhesive tape remains in a whisker shape. When remained adhesive tapes are stacked, the thickness of the adhesive tapes increases in the portion and it may cause a problem in following processes such as a process of separating the protective tape from the surface of the wafer and a wafer process such as a dicing process.
In the technique disclosed in JP-A 11-3876 (1999), a needle member is used as the cutter for cutting the adhesive tape so that the cutting path does not remain in the ring frame so much. Therefore, the ring frame can be used a plurality of times. In recent years, however, as the diameter of a wafer increases and the thickness of the wafer decreases, there is a trend that the thickness of the adhesive tape for dicing increases and the rigidity of the adhesive tape increases. Consequently, it is difficult for the needle-shaped cutter as described in JP-A 11-3876 (1999) to cut the adhesive tape so that the cutting start point and the cutting end point meet are made coincide with each other. In the case of using a knife-shaped cutter or a round-blade cutter which has been conventionally used, the cutter enters the cutting path formed in the past cutting operations at the time of cutting as described above. It becomes difficult to accurately cut the adhesive tape in a circular shape and, in some cases, the adhesive tape remains in a whisker shape at the cutting start point and the cutting end point.